This invention relates, in general, to a communication system architecture and a method for establishing a communication, and is especially applicable to the interconnection and signalling requirements of a switch fabric interface that couples a narrowband network to broadband functionality. The present invention is particularly, but not exclusively, applicable to a connection regime that effectively connects communication traffic on a trunk circuit in the synchronous domain to a packetised data environment supported on virtual circuits of an asynchronous domain.
Globally, telecommunication systems are, generally, in a transitional phase between second generation, narrowband digital networks (such as the Global System for Mobile (GSM) cellular communication system) and future, multi-media digital networks (such as the Universal Mobile Telecommunication System (UMTS)) having broadband capabilities. This transition is necessarily required to support higher data rate communications, including video and Internet applications, presently being proposed and made available.
Unfortunately, this transitional phase also presents system operators with several dilemmas, and prejudices immediate implementation of such broadband systems. For example, until such a time when a free-standing broadband system becomes an accepted and freely available standard for all subscriber terminals (such as cellular telephones and data transmission devices), system operators are reticent to write-off their significant investments in current narrowband infrastructure technology. Indeed, such narrowband infrastructure technology already provides a rich set of services and service creation environments that would have to be re-implemented for deployment in broadband networks. Consequently, present-day narrowband systems must be adapted to accommodate both narrowband and broadband users; with this statement particularly relevant to service and system management, call establishment and inter-working procedures between these different forms of network.
For an effective migration between narrowband and broadband systems (for the transitional phase), system operators must particularly consider an inter-working scenario when all subscribers connect to a narrowband network, but one or more intermediate broadband networks are used to relay information between these narrowband subscribers. Any interim solution should also optimise service and system management, while also providing infrastructure equipment that can be re-used in a fully-fledged broadband environment.
In more detail, telecommunication networks comprise nodes connected by communication resources (usually termed xe2x80x9clinksxe2x80x9d), with a particular network technology characterised by the means of transmission of user and control information along these links and also by the routing and relaying functions embodied in the nodes. The term routing is used to describe the process of determining the path the information will take through the network, while relaying is the process of transferring information from one link to another, i.e. the information is merely passed, without alteration, from one channel resource to another. Routing and relaying functions are therefore core to the development of an efficient system having optimised service capabilities, with operator profits and subscriber service charges inherently entwined with such optimisation.
Taking GSM as an exemplary form of a narrowband digital network, user and control information (or xe2x80x9cdataxe2x80x9d) is interleaved, using time division multiplexing (TDM), on a 64 kbit per second (kbps) pulse code modulated (PCM) bearer channel. Indeed, these bearer channels can each be framed to support four voice calls of 16 kbps, comprised from 13 kbps of sampled and encoded speech and 3 kbit/s of ancillary information, such as parity check and correction bits (and the like) and synchronisation information. Data is then relayed across a node by some form of synchronous TDM switching fabric, often of the xe2x80x98time-space-timexe2x80x99 type. Control information (e.g. call set-up and tear-down messages) logically follows the same path (although not always the same physical path) through the network as user information, and is terminated in each node for routing purposes. Routing is conventionally performed, in each node, on a xe2x80x98hop-by-hopxe2x80x99 basis using long lived routing tables, i.e. the node is sufficiently intelligent to determine an optimum route for the succeeding network connection.
Control information is regulated by a signalling scheme that is distinctive to the type of network employed. Particularly, public signalling systems are used between nodes of a public network and between public networks of different operators. Signalling System No. 7 is the only important example of a public signalling system. Access signalling systems are used between subscribers and edge nodes of public networks, e.g. between a radiotelephone and a base station subsystem (BSS). In fact, the most common digital access signalling schemes are Common Channel Signalling Systems, such as the Integrated Service Digital Network (ISDN) DSS1 signalling schemes (and its predecessors) and Channel Associated Signalling schemes that are both derived from analog signalling. Private schemes are generally derived from access schemes but provide richer functionality within personal networks, such as within a secure private branch exchange (PBX).
On the other hand, broadband digital networks are characterised in that user and control information is transmitted in fixed or variable length xe2x80x9cpacketsxe2x80x9d or xe2x80x9ccellsxe2x80x9d, with these packets prepended with headers that contain bearer channel identification. In contrast with narrowband systems, user information is relayed across a node via an asynchronous switching fabric that examines each packet in turn (using some kind of fairness algorithm) and directs it to the appropriate output link in response to the input link and bearer channel identification. Routing and control information transmission is, however, similar to that for the narrowband case, and differs only inasmuch as the signalling schemes are technology specific.
Another significant problem associated with prior art narrowband-broadband interfaces arises with architectural change. For example, the introduction of new or up-graded infrastructure can have unwanted ramifications throughout the entire communication system because changes in the inter-working relationships between the network controller (e.g. a call server) and the narrowband-broadband interface can potentially alter network identities and addresses. More particularly, the configuration of the narrowband-broadband interface may change (as a result of either the inclusion of additional equipment, the up-grading of existing equipment, or the failure of a particular system entity), while the call server remains oblivious to this change because of the uniform fabric application interface between the call server and the fabric control software. Consequently, the system (generally) may not necessarily be exploited and optimised to its greatest potential. Network providers may therefore also be discouraged from implementing the further development of existing networks since global system changes may be required, with such system changes being both time consuming and complex in nature.
To facilitate use of broadband networks and the migration of communication networks to high data rate technologies (e.g. the 2 Mbps rate envisaged within UMTS), there is a need to provide an effective mechanism for interconnecting narrowband networks through a transparent broadband ether, while also providing an easy migration to more advanced systems. Moreover, to encourage subscription to broadband services, operators must provide a reliable but relatively low-cost (and hence optimised) communication system architecture. Furthermore, the broadband ether must accommodate and support narrowband signalling schemes without effecting either data integrity or in any way inhibiting data flow or interconnection.
One particular and prominent disadvantage or drawback associated with the interworking and interconnection of narrowband networks with a broadband backbone is that there is a significant time and processing overhead associated with actually establishing the physical connection between the different networks. Specifically, the ATM Forum User Network Interface (UNI) can be considered both to define a reference point within a system architecture (especially in the context of an interface between an ATM switch fabric and either a narrowband network or a broadband network), and also the requisite signalling protocols for traffic and control information. In other words, UNI defines the system (particularly the interface) connectivity and interworking function between the different portions of the system. For example, with respect to a network access peripheral that provides coupling of narrowband trunk circuits to the ATM switch fabric, UNI may define ATM adaptation layer 1 (AAL-1) for traffic and Q.2931 for signalling.
Presently, the requirements imposed in the UNI necessarily demand a plethora of request and response messages signals to sent over a signalling channel dedicated to support the numerous call processing functions; with these messages determining the form of the connection and ultimately identifying the route for the connection. Indeed, UNI stipulates that the assignment of virtual channel identities (VCIs) and virtual path identities (VPIs) is accomplished through negotiation between an ATM entity and the ATM network proper. As such (and in relation to existing interfaces between narrowband and broadband networks), UNI demands that an ATM switch fabric (for example), in response to a connection request on an in-coming port, routes the request (in an appropriate form) to the broadband (ATM) network. The switch fabric must then await a response from the ATM network indicating an assigned VPI/VCI (virtual path identity/virtual circuit identity) for the voice/data call; the switch fabric can then associate the assigned VPI/VCI to an output port that acts to interface the switch fabric to the broadband network. The switch fabric then records this assigned VPI/VCI with the input VPI/VCI, as an association. Finally, the switch fabric executes an internal cross-connect between the identified input and output ports (by virtual of being able to resolve the respective VPI/VCI assignments and hence to enable an interworking function) to establish connection of the narrowband trunk to the ATM network.
The elimination of specific signalling demanded by UNI in the connection establishment procedure would clearly result in both a faster call connect and a function that was less processor intensive. However, such elimination of control signalling overhead should not jeopardise the compliance of any such modified interface with respect to an established Technical Standard, nor should its adoption significantly disrupt the configuration of installed infrastructure.
According to a first aspect of the present invention there is provided a method of communicating information between narrowband circuits and broadband channel resources across an interface having a processor for controlling connection therebetween and an associated memory, the method comprising the steps of: pre-provisioning connection paths between narrowband circuits and broadband channel resources and storing these pre-provisioned connection paths in memory as connection identifiers; and in response to the interface receiving an instruction to connect narrowband circuits and broadband channel resources, having the processor establish a connection path using available pre-provisioned connection identifiers.
The connection identifiers associate port addresses of the interface to pre-provisioned connection paths.
In a preferred embodiment, the method further comprises at least one of the steps of: pre-storing VPI/VCI information pertaining to end points of a cross-connect and establishing a connection between a narrowband trunk to a pre-provisioned network virtual channel connection (VCC) using the stored VPI/VCI information; and establishing a cross-connect to a virtual channel by first determining a VPI/VCI of a demand assigned channel connection.
In another embodiment, at least one call server administers the set-up of a call and the method further comprises the steps of: using a generic end point as a termination point of the switch responsive to a call server associated with a called party; and establishing the virtual channel connection for an inter-node trunk based on the generic end-point.
In another aspect of the present invention there is provided an interface of a wireline communication system arranged to interconnect narrowband circuits and broadband channel resources, the interface comprising: a memory containing a plurality of connection identifiers defining pre-provisioned connection paths between narrowband circuits and broadband channel resources; and a controller associated with the memory and arranged to control a call connection within the interface in response to call connect instructions, the controller configured to access the pre-provisioned connection identifiers to identify an available connection path and, in response thereto, to establish the call connection using the available connection path.
In a further aspect of the present invention there is provided a hybrid narrowband-broadband wireline communication system comprising: a) at least one call server that administers the set-up of a call supported on narrowband trunks and broadband channel resources; b) an interface, coupled to a call server, arranged to interconnect the narrowband trunks and broadband channel resources of the hybrid narrowband-broadband wireline communication system, the interface further comprising: a memory containing a plurality of connection identifiers defining pre-provisioned connection paths between narrowband trunks and broadband channel resources; and a controller associated with the memory and arranged to control call connection within the interface, the controller configured to access the pre-provisioned connection identifiers to identify an available connection path and, in response thereto, to support the call using the available connection path.
Advantageously, the present invention provides a communication system architecture that can operate across mixed nodes having narrowband and broadband capabilities to establish efficiently and quickly a through-path or an end-to-end connection. For example, the through-path might be from a calling party or a network adaptor of an interface to a called party (such as another subscriber terminal or an intelligent peripheral, e.g. a network gateway to value added services), or may need to be established in-call to support a new connection or routing function.
In another aspect of the present invention there is provided an interface coupled to a call server arranged to administer call connection in a communication system, the interface comprising: a connection broker responsive to the call server and arranged to facilitate interconnection of a call through the interface; at least one network adaptor coupled to the connection broker, the at least one network adaptor providing access to at least one narrowband trunk; and a switch fabric coupled to the at least one network adaptor and responsive to the connection broker, the switch fabric providing access to a plurality of broadband channel resources; wherein the connection broker is arranged to direct separate and functionally distinct service logic to the switch fabric and the plurality of network adaptors.
Beneficially, the system architecture of present invention can support simplified signal processing at the network adaptor and the switch fabric by virtue of functionality being more effectively partitioned. Specifically, a processor of the network adaptor can be simplified by restricting its performance to, principally, voice processing features, such as echo cancellation and through-path control, while a switch fabric performs dedicated space switching, e.g. scaling and connectivity functions between a narrowband node and a broadband network.